The proposed research will investigate the fundamental properties of resistance vessel smooth muscle in normal, prehypertensive, and hypertensive animals. The hypertensive state will be spontaneous in spontaneously hypertensive rats (SHR) or will be brought about experimentally by administration of deoxycorticosterone and salt feeding and by renal artery clamping. At least two strains of normal rats will be used as controls. Mechanical studies of the smooth muscle, specifically on the duration of active state, will be performed to elucidate the type of contractile behavior of normal and hypertensive resistance smooth muscle. Ca45 efflux studies are proposed for compartmental analysis of calcium storage, while isolated microsomal fractions will be studied for the mechanism of calcium uptake and binding by sarcovesicular structures. Characteristics of the calcium control system at the level of the regulatory proteins (myosin vs. troponin) will also be studied as will the proteins of the thick and thin filaments.